Particle sorter with segregation indicator

ABSTRACT

Small particles to be sorted are entrained in a stream of fluid and particle differences are detected to control a sorting means located downstream. The sorting means is effective to switch the particle carrying fluid to two different paths determined by the particle differences to thereby accomplish the sort. A photoelectric particle detector is positioned to detect the passage of particles through one of said paths in order to verify that the sorting operation has occurred.

United States Patent 1191 Kamentsky et a1.

PARTICLE SORTER WITH SEGREGATION INDICATOR Inventors: Louis A.Kamentsky, Briarcliff Manor; Isaac Klinger, Yorktown Heights, both ofNY.

Assignee: Bio/Physics Systems, Inc., Mohapac,

Filed: Mar. 5, 1973 Appl. No.: 338,215

US. Cl 209/1ll.7, 137/815, 210/85, 250/222 CP, 324/71 CP,'356/39 Int.Cl. B07c 5/342 Field of Search 209/4, 3, 74, 111.6, 111.7, 209/111.8;324/34, 61, 71 CP; 137/815; 356/39; 210/65, 85; 250/222 CP; 235/92 V, 92PC References Cited UNITED STATES PATENTS Hutchison 235/92 PC 1 Aug. 6,1974 3,269,419 8/1966 Dexter ..137/s1.5 3,362,421 1/1968 Schaffer..137/s1.5 3,508,654 4/1970 0136611 ..210/s5 3,508,655 4/1970 Kamentsky..210/s5 3,560,754 2/1971 Kamentsky ..209/111.5 3,710,933 1/1973Fulwyler ..209/3 Primary Examiner--L1oyd L. King Assistant Examiner-GeneA. Church Attorney, Agent, or Firm-Curtis Ailes 571 ABSTRACT Smallparticles to be sorted are entrained in a stream of fluid and particledifferences are detected to control a sorting means located downstream.The sorting means is effective to switch the particle carrying fluid totwo different paths determined by the particle differences to therebyaccomplish the sort. A photoelectric particle detector is positioned todetect the passage of particles through one of said paths in order toverify that the sorting operation has occurred.

9.9!39 15 4213 1199 Fi 'i i PATENIEDMIE M914 3182?; 555

SHEET 1 0F 3 50 amp PATENTED 51974 3.827. 555

SHEET 2 BF 3 FIG.2

This invention relates to apparatus for sorting small particles such asbiological cells which may be microscopic in size. More particularly,the apparatus is capable of sorting such particles having differentcharacteristics into different containers or receptacles with a highdegree of accuracy.

In recent years, accurate high speed machines have been devised formeasuring and indicating various characteristics of small particles suchas biological cells. One such machine is described and claimed, forinstance, in US. Pat. No. 3,705,771 dated Dec. 12, 1972 for aPI-IOTOANALYSIS APPARATUS, and assigned to the same assignee as thepresent application. However, there is a continuing important need for amachine which will very accurately and very rapidly sort such particlesinto two or more groups having different characteristics. This sortingfunction is particularly needed for purposes of medical diagnosis, andfor medical research. There are many different particle characteristicswhich can be the basis for the sorting or segregation. The sorting isparticularly valuable in instances where the particles or cells havingthe unique characteristics are present in a very small proportion to thetotal, making it difficult to obtain information about the uniqueparticles without physically separating those particles from the mainbody of particles in which they occur.

The present invention is particularlyuseful in conjunction withapparatus disclosed in patent application Ser. No. 338,216 filedconcurrently with the present application by Mitchell Friedman, now US.Pat. No. 3,791,517 issued Feb. 12, 1974, for a DIGITAL FLU- IDICAMPLIFIER PARTICLE SORTER and assigned to the same assignee as thepresent application. The present invention is disclosed in combinationwith the apparatus of the above-mentioned copending application, but itis understood that the present invention is also useful in combinationin other sorting apparatus.

One of the most serious problems in particle sorters for very smallparticles is the difficulty in determining whether or not the apparatusis operating correctly to provide the desired segregation of sortedparticles. This problem is particularly serious with particle sorterscapable of vary rapid operation.

Accordingly, it is one object of the present invention to provide animproved particle sorter which incorporates means for verifying that thesorting operation has taken place.

In particle sorting apparatus, the mode of operation may include theentrainment of the particles to be sorted in a stream of fluid,detection of differences in particle characteristics as the streampasses a detection station, and then transmission of the resultantdetection signals to a sorting means located downstream of the detectionstation. The precise timing of the signals to the sorting means from thedetection station is vital to the accurate operation of the apparatus.The required timing is dependent upon the velocity of the particlecarrying fluid stream.

Accordingly, it is another object of the present invention to provide ameans for indicating the duration of the interval for the passage of aparticle from the detection station to the sorting means in order todetermine the exact timing for the operation of the sorting means.

Further objects and advantages of the invention will I be apparent fromthe following description and the accompanying drawings.

In carrying out the invention there is provided an improved particlesorting apparatus for sorting very small particles comprising a housingdefining a detection chamber with means for moving a fluid in which theparticles are suspended through said housing in a stream. A detectionmeans is associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics. A sorting means is positioned downstream fromsaid detection chamber housing, said sorting means being connected tosaid detection means and being operable in response to said electricalsignals from said detection means to segregate particles havingpredetermined differences in particle characteristics from the streamof, particles. Said particle sorting means defines at least twoalternate paths of egress of particles therefrom, one of said pathsrepresenting particles segregated thereby and the other of said pathsrepresenting particles not to be segregated from the stream. Theapparatus includes the combination of a light source and a photoelectricdetector associated with one of said paths to determine the passage ofparticles therethrough in order to verify the sorting operation of theapparatus.

In the accompanying drawings:

FIG. 1 is a schematic side view, partly in section, illustrating apreferred embodiment of the invention.

FIG. 2 is a representation corresponding to FIG. 1, but showing analternative embodiment of the inven-- tion.

FIG. 3 is a simplified schematic diagram illustrating a modification ofthe invention employing a plurality of fluidic amplifiers.

FIG. 4 is a simplified schematic diagram illustrating a modification ofthe invention employing a plurality of combinations of detectionchambers and digital fluidic amplifiers connected in tandem.

Referring more particularly to FIG. 1, there is shown an optical chamberformed by a glass tube member 10 which is clamped by means not shown toa digital fluidic switch chamber housing member 14, the two membersbeing sealed together by a liquid-tight annular seal 18. The liquid 19containing the particles to be observed enters the apparatus through atube 20 centrally disposed within the funnel-shaped entrance portion 24of the cylindrical central bore 26 of the member 10.

Another liquid 23 also enters the mouth 24 of the central bore 26 andforms a sheath of liquid for the liquid 19 containing the particles.

The velocity and volume of flow of the particlebearing liquid 19 and thesheath liquid 23 entering the mouth 24 of the central bore 26 are suchas to cause the stream of particle-bearing liquid to be narrowed down,as shown at 28, into a very narrow stream 29 having a maximum dimensionof the same order of magnitude as the maximum dimension of the particlesbeing carried by the stream. For instance, this dimension may be in theorder of 25 microns. The particles of greatest interest are oftensomewhat smaller than this, being in the range from 1 to 10 microns indiameter. The funnel-shaped entrance portion 24 of the cylindricalmember is preferably provided with an exponential function shape toprovide for smooth nonturbulent flow of the liquids at the criticalposition 28 where the particle-carrying liquid is narrowed down.Typically, the particle-carrying liquid may be an aqueous solution andthe'sheath liquid 23 may be water.

The stream 29 of particles is illuminated by a beam of light emitted bya light source 30 which preferably consists of a laser together with anappropriate system of lenses as described more 'fully in theabovementioned patent. One satisfactory type of laser, for instance, isa helium-neon laser. The laser and the associated lenses provided a verynarrow beam in which the pattern of the illumination of the beam atpoint 38 where it strikes the particles is preferably a very narrowellipse which appears to be a thin line of light transverse to thestream of particles.

Electrical photoresponsive pick-up elements are arranged around theoutside of cylindrical chamber member 10 to detect different opticalreactions of each particle to illumination from the beam. These elementsare illustrated at 40, 42, 44, 47, and 48 which are all connected toprovide signals to an apparatus 46, and elements 50 and 52 connected toprovide signals to apparatus 54. The apparatus 54 may be combined withthe apparatus of 46, but is separately shown to simplify the drawing.The apparatus 46 may include amplifiers, logic circuitry, digitalcounters, and electronic display devices. The circuits within theapparatus 46 may be carried out in accordance with the teachings of aprior U.S. Pat. No. 3,662,176 issued May 9, 1972 on an invention ofLouis A. KameniSky and Isaac Klinger for A PHOTO-OPTICAL PARTICLEANALYSIS METHOD AND APPARATUS which is assigned to the same assignee asthe present application. The apparatus 46 is sometimes referred tohereinafter as circuits 46.

When a unique particle characteristic is detected which signifies thepresence of a unique particle which is to be segregated from the otherparticles, the detection circuits 46 send out an electrical signalthrough a delay circuit 49, a gate circuit 51, and connections 56 to anelectrical transducer 58 which is mounted within the fluidic switchhousing 14. This causes a switching of the particle-carrying stream fromone outlet port to another.

The fluidic amplifier housing 14 defines a switching chamber 60 having afirst outlet port 62, and a second outlet port 64. The flow of liquidthrough the optical chamber 10 is in a laminar (non-turbulent) mode. Inthe absence of a signal at the transducer 58, the stream of fluidemanating from the bore 26 of the chamber It) continues to flow in alaminar mode into the inlet 66 of the fluidic amplifier housing 14, andcontinues in the laminar mode through the switching chamber 60, and outthrough the first outlet port 62, which is in direct axial alignmentwith the inlet 66. However, when the transducer 58 is energized, itinduces turbulence into the liquid stream. In the presence ofturbulence, the stream tends to attach itself to the nearest side wall68. This wall attachment effect causes the stream to follow the sidewall 68 to the second outlet port 64.

The wall attachment effect is sometimes referred to as the Coanda effectin honor of the Rumanian engineer, Henry Coanda, who discovered it. Thiseffect is well recognized in the literature as the basis for manyfluidic digital switching devices. The wall attachment effect is causedby a bubble of low pressure adjacent to the exit of the nozzle formed bythe inlet 66 at the beginning of the near side wall 68. This lowpressure bubble causes the stream of liquid to bend towards the wall 68and to become stable in this deflected course of travel. Thus, as longas the stream remains turbulent, by reason of the application of asignal to the transducer 58, the stream remains deflected to the secondoutlet port 64. However, upon the discontinuance of the signal totransducer 58, laminar flow is reestablished, the wall attachment effectdisappears, and the stream returns to the first outlet port 62.

The speed of operation of the circuits 46 in providing a signal to thetransducer 58 is properly correlated with the speed of the liquid streamof particles and the dimension between the optical detection point 38and the transducer 58 to provide for switching of the desired particlesfrom port 62 to port 64. The dynamic response in the speed of operationof the fluidic switch is also a factor. For this purpose, the delaycircuit 49 is provided between the circuits 46 and transducer 58. Thedelay circuit 49 may be adjustable to properly correlate the timing ofthe signal to transducer 58 with the arrival of-the particle to beswitched by the transducer. One of the important advantages of thispreferred embodiment of the invention is that the response of the systemis extremely rapid since the transmission of signals is accomplishedentirely electrically to the very point in the inlet 66 of the fluidicswitch where turbulence must be induced. This is in contrast to otherfluidic switches in which a signal is transmitted through a column offluid to the control point.

The transducer 58 is preferably a piezoelectric crystal which is capableof physical deformation in re sponse to an applied voltage. Theexcitation signal applied to the crystal 58 is preferably an alternatingcurrent at a frequency corresponding to the natural resonant frequencyof the crystal 58 and its surrounding fluid soas to provide maximummechanical output in response to the available electrical input energy.Thus, the individual signals applied to the transducer 58 are usually inthe form of bursts of alternating current gated by gate 51 from anoscillator 53. The resultant alternating mechanical changes in thepiezoelectric crystal 58 are very efficient in inducing turbulence inthe liquid stream so as to assure immediate initiation of the wallattachment effect.

While the transducer is shown as embedded in a side wall of the inletnozzle 66 of the fluidic amplifier on the same side as the wall 68, itwill be understood that the transducer may be effective also in otherlocations communicating with the inlet 66, or in the switching chamberin close proximity to inlet 66. The piezoelectric crystal is preferredas the transducer for this purpose. However, other types of transducers,such as electromagnetically energized acoustic vibration transducers maybe employed.

The optical chamber member 10 is a glass tube having a cylindrical innerbore 26. However, the interior cavities of the digital fluidic amplifierdefined by the housing 14 may be circular or non-circular incrosssection, or essentially two-dimensional in nature. Thus, the inlet66 may include a transition from a circular shape to a rectangularshape, or the inlet 66 may simply be rectangular in shape throughout itslength, having a minimum cross-sectional dimension which is at least asgreat as the diameter of the bore 26 of the optical chamber 10. Thetransition of the stream of liquid from the circular cross-section bore26 to the rectangular inlet 66 of the fluidic amplifier does not disturbthe flow sufficiently to create turbulence. Thus, the stream retains itslaminar-characteristic until it is made turbulent by the transducer 58.The interior cavities of the housing 14 can be rounded at the corners,and the inlet 66 and the outlet ports 62 and 64 can actually be circularin cross-section without interfering with the operation of the device asdescribed above.

The ports 62 and 64 are connected to suitable collectors or containers,not shown. Either, or both, of the separate collected cell bearingliquids can be run through the apparatus again to accomplish anadditional refinement in the sorting operation by again sorting for thesame characteristic, or for still another characteristic. After a run iscompleted, the apparatus may be flushed with a saline solution or water.To assure complete collection of all of the unique cells sorted at port64, flushing liquid may be applied at the inlet 23 while outlet port 62is blocked so that all of the flushing liquid is necessarily directedthrough the outlet port 64,

carrying any sorted particles which remained in the port 64 and theassociated passage to the collector or container associated with thatport. The apparatus is then preferably completely flushed to preventcontamination of a new sample with the remains of a completed sample.

A number of different characteristics of the particles may be opticallydetected in the chamber 10 and used as a basis for the sorting of theparticles. For instance, the electrical photoresponsive pick-up element40 is arranged in direct line with the beam to measure the degree ofextinction of illumination by each particle. In the absence of aparticle at the intersection of the beam, or in the absence of anysubstantial extinction, the beam strikes the element 40 without anysubstantial diminution.

As illustrated in the drawing, the beam diverges to a certain extentafter having been converged at the center of the chamber at 38. Theeffective divergence in a practical embodiment has been limited toapproximately one degree on each side of the center line of the beam asmeasured from the particle scanning point 38 at the center of thechamber. Thus, photoresponsive pick-up elements 42 and 44 are arrangedon opposite sides of the direct beam and can be used to measureillumination scattered out of the direct beam by the particles over aselected range of angles from l up to a predetermined angular limit. Forinstance, this range of angles may be from 1 to 9. As shown in thedrawing, the photoresponsive pick-up elements 42 and 44 may beelectrically connected in parallel so that electrical signals resultingfrom illumination scattered on either side of the beam and detected byelements 42 and 44 will be registered at the electrical apparatus 46.Additional pairs of photoresponsive pick-up elements for detectingscattered light at other ranges of angles may be provided as shown at 47and 48. For instance, this additional pair of pick-up elements maydetect scatter over the scatter angle range from 9 to 22.

Scattering of illumination from the particles in the reverse direction,called back scattering can also be detected by photoresponsive elements50 and 52 arranged on the same side of the chamber as the light sourceand connected in parallel to an electrical pick-up and recordingapparatus 54. Apparatus 54 may be combined with the apparatus 46, but itis shown separately here to simplify the drawing.

The portion of the apparatus for detecting different particlecharacteristics as just described above may preferably be carried out inaccordance with the teachings of the patent first mentioned above. Inaddition to detecting different particle characteristics by extinctionand by scatter, distinctive particle characteristics may also bedetermined on the basis of fluorescent radiation reactions from theparticles to illumination of the particles as taught in that priorpatent. When fluorescent radiation reactions are desired, an argon ionlaser may be used as the source of illumination. Furthermore,sophisticated combinations of particle measurement characteristics maybe employed for controlling the particle sorting operation. Forinstance, electrical summations or differences of different signals maybe employed at selected threshold values for determining when a particleshould be segregated from the main stream. Such circuits are describedin the aforementioned U.S. Pat. No. 3,662,176.

The features described above in connection with FIG. 1 are common to theabove-mentioned concurrently filed patent application, now U.S. Pat. No.3,791,517. The remaining features described immediately below inconnection with FIG. 1 are particularly important and unique withrespect to the present invention.

A source of illumination such as a small incandescent lamp is provided,as indicated at 55, which directs a beam through a central slit in anoptical mask 57 and thus through the particle carrying stream to anoptical pick-up element, or photocell, 59. The optical pick-up element59 is connected to an amplifier 61 which may be connected at 63 tocontrol the variable delay circuit 49. The illuminationfrom the lamp 55traversing the particle stream to the photoelectric pick-up element 59is effective to detect the passage of particles in the particle stream.Since this combination including pick-up 59 is located near thetransducer 58, it is in a position to measure the arrival of theparticle upon which the transducer 58 is intended to be effective, andto thus measure the travel time of the particle from the initialdetection point 38 to the transducer 58.-

While the pick-up element 59 is not located at the identical position ofthe transducer 58, the travel time of particles from point 38 to pick-upelement 59 is proportional to the travel time from point 38 to thetransducer 58 so that the interval until the arrival of particles atpick-up element 59 is a measure of the travel time to the transducer 58.Thus, the signals from pickup element 59 amplified by the amplifier 61may be.

used to control the delay circuit 49 to provide an exact match of theoperation of the electrical circuits energizing transducer 58 with thevelocity of the particlecarrying liquid. This provides an importantenhancement in the precision and accuracy of operation of the sorter.

In accordance with another feature, another light source in the form ofan incandescent lamp 65 provides a beam of light through a slit in anoptical mask 67 which crosses the passage for port 64 to a photoelectricpick-up element 69 which is connected to an amplifier 71. By means ofthis apparatus associated with the photoelectric pick-up 69, the passageof a particle through the port 64 can be detected so as to positivelyindicate that the sorting operation has been successfully accomplishedwith respect to that particle. A very useful means for indicating thissuccess is a cathode ray oscilloscope 73 which is connected through aswitch 75 to receive the amplified sort indication signal from theamplifier 71, preferably as a vertical deflection on the oscilloscope.

In order to provide a correlated horizontal sweep, the scope 73 ispreferably connected through a connection 77 to receive from thecircuits 46 an indication of the passage of the particle at the originaldetection point 38, the signal on 77 being used to trigger theinitiation of the horizontal sweep on the scope 73. Thus, the verticaldeflection caused by the signal from amplifier 71 will occur at apredictable horizontal position on the scope 73 which is related to thevelocity of the particlecarrying liquid through the apparatus.

Alternatively, a similar detection of the passage of particles to theport 62 may be accomplished by the combination of a lamp 79, anapertured mask 81, a photoresponsive pick-up element 83, and anamplifier 85 connected thereto. The switch 75 is arranged to select theoutput from amplifier 71 or from amplifier 85 for indication on theoscilloscope 73.

Thepick-up 83 for port 62 may be used to indicate that the particlespassing through the port 62 have not been selected to be segregated intoport 64. For instance, the apparatus may be checked for proper sortingoperation by introducing a sample in which all particles are of a classwhich should be segregated into the port 64. With such a sample,whenever the sorting operation is begun, vertical deflections on theoscilloscope 73 derived from the pick-up element 83 for port 62 shoulddisappear completely.

The signal from the pick-upelement 83 may also be employed in place ofthe signal from pick-up element 59 forv controlling the delay circuit49. Assuming that the main body of particles in the initial liquidstream continues on through the discharge port 62, the time interval oftravel of an individual particle from the initial detection point 38 tothe vicinity of the pick-up element 83 will be a predictable function ofthe interval for the travel of an individual particle from point 38 tothe transducer 58. Accordingly, the measurement available from pick-upelement 83 is an appropriate signal for controlling the delay circuit 49in order to properly time the gating of the signals to the transducer58. The pick-up element 59 and the associated apparatus may be omittedfrom the system if the signal from pick-up element 83 is used to controlthe delay circuit 49.

It is not absolutely necessary, in order to obtain the advantages ofthese features to have a direct connection, such as connection 63, fromone of the pick-up amplifiers to control the delay circuit 49. In otherwords, an open loop system may be employed in which the delay intervalis measured, such as by the indication on the oscilloscope 73, and thatmeasurement is then used to manually set the delay on the variable delaycircuit 49. However, the direct connection 63 from the amplifier 61 tothe delay circuit 49 provides the advantage of continuous and automaticadjustment of the delay to compensate for any fluctuation in thevelocity of the particle-carrying stream.

ln accomplishing the purposes of the pick-ups 69 and 83 in indicatingthe accomplishment of the sort function, it may also be useful to havecounters attached for actuation fromthe amplifiers 71 and 85 forindicating and storing a registration of the numbers of the particleswhich have been sorted into the respective ports 62 and 64. It iscontemplated that the circuits 47 may include counters for counting thetotal number of particles and also for counting particles having uniquecharacteristics to be detected and upon which the sort is to be based.Accordingly, the counters attached to the amplifiers 71 and whichindicate the numbers of particles sorted into the two channels can becompared with the counts registered by the counters within the apparatus46 to accurately determine the efficiency of the sorting operation.

It will be understood that the pick-up elements 59, 69, and 83, and theassociated apparatus, are shown schematically in order to simplify andclarify the drawing. In a preferred embodiment of the invention, each ofthese combinations of apparatus is preferably rotated about the axis ofthe associated liquid channel so that the direction of the light beam ineach instance is directly perpendicular to the plane of the sectionshown in the drawing. Thus, in such a preferred arrangement, the pick-upelement 59, for instance, would appear on the wall of the inlet 66directly behind the liquid stream. In such a preferred physicalembodiment, the lamp 55 and the pick-up 59 can be arranged andpositioned exactly at the axial position of the transducer 58 within theinlet 66 so as to provide an exact measurement of the interval until thearrival of a particular particle at the transducer 58.

The switching chamber 70, and the ports 62, 64, and 66 may preferably beformed by providing the chamber housing 14 in two parts, one partcontaining cavities to provide the chamber and ports, and the other partconstituting a cover which is attached over the other part to enclosethe cavities. Thus, the part of the housing 14 containing the cavitiesmay contain the pick-up elements 59, 69, and 83 in the back wallsthereof, and the light sources 55, 65, and 79, together with theirassociated optical masks, may be attached to, or be a part of, the covermember. These positions may, of course, be reversed.

Other modifications are also possible. For instance, fiber optics may beemployed to carry the illumination from a lamp, such as S5, to thechannel, such as 66, where it is needed. Instead, or in addition, fiberoptics may be used to convey the light beam from the channel 66 to thephotoelectric pick-up 59. The use of fiber 0ptics may be particularlyadvantageous because of the space limitations in the vicinity of thechannels being monitored, the optical fibers requiring much less spacethan the lamp and photoelectric pick-up elements. Also, light sourcesother than incandescent lamps may be employed.

In order to simplify the drawings and descriptions of the modificationsof the invention illustrated in FIGS. 2, 3, and 4, the pick-up elements59, 69, and 83, and the associated apparatus, are not illustrated ordescribed in connection with these other figures. However, it will beunderstood that the principles of the features associated with thesepick-up elements are equally applicable to these modifications. Forinstance, in FIG. 2, three outlet ports are provided from the switchingchamber and it will be understood that photoelectric sort detectors,such as elements 69 and 83, may be employed for each of those threeoutlet ports.

FIG. 2 illustrates an alternative embodiment of the invention in whichthe switching chamber 60 is modified as shown at 60A, in a modifiedfluidic amplifier housing 14A, to provide an additional outlet port 70and added control ports 72 and 74. A control fluid under pressure may besupplied to the switching chanber 60A through the control ports 72 and74 through the respective supply lines 76 and 78 under the control ofelectromagnetically operated valves 80 and 82. These valves may becontrolled from the apparatus 46 through the electrical connectionsrespectively indicated at 84 and 86.

As illustrated in the drawing, the opposite walls 68 and 69 of theswitching chamber 60A are essentially equidistant from the nozzle formedby the inlet 66. Accordingly, they are equally capable of displaying thewall attachment effect in the presence of turbulence in the liquidstream, as previously described above. Thus, just as the wall attachmenteffect to wall 68 directs the liquid stream to outletport 64, the wallattachment effect at wall 69 leads the fluid stream to the outlet port70. Once established at one wall, the wall attachment effect will bemaintained and will hold the stream to one of these two walls, and thusdirect the stream to one of these two outlet ports, as long asturbulence continues. In order to determine which direction the streamwill take, a signal must be supplied from one of the control ports 72 or74. If the signal takes the form of a supply of control fluid underpressure, it has the effect of shifting the stream away from the walladjacent to the control port and over to the opposite wall. Thus, ifcontrol fluid is supplied to the switching chamber 68 through thecontrol port 74, the supply of fluid destroys the low pressure bubble atthe wall 69, causing the stream to shift to the opposite wall 68. Asimilar, but opposite effect is available if a vacuum is applied at thecontrol port 74. This reduces the pressure at the wall 69, tending toincrease the wall attachment at the wall 69 and to switch the device sothat the liquid stream is pulled away from the wall 68 and to the wall69 and to the port 70.

The embodiment of FIG. 2 is capable of several different alternativemodes of operation. For instance, if the switching chamber 60A isfabricated in an asymmetrical form such that the wall 68 issubstantially closer to the nozzle formed by the inlet 66 than the wall69, then without any control signals at the control ports 72 and 74, theswitching action will be identical to that described above for theembodiment of FIG. 1. Thus, if a signal is supplied to the transducer58, the resulting turbulence will cause the stream to attach to the wall68 and to be directed to port 64. In the absence of a signal. attransducer 58, the laminar flow will continue, and the stream will bedirected through the outlet port 62.

However, with the asymmetrical configuration, if a fluid pressurecontrol signal is applied at the control port 72 while the turbulentcondition exists by reason of the operation of the transducer 58, thenthe wall attachment effect at wall 68 will be discontinued, and thestream will attach to wall 69, even though that wall is more distantfrom the nozzle formed by inlet 66. Thus, in such an arrangement, withan asymmetrical configuration, the second control port 74 is notnecessary to provide a three way switching effect to the three outletports 62, 64, and 70. Summarizing the operation of such an asymmetricalform of the invention: with neither the transducer 58 nor the controlport 72 being effective, laminar flow continues, and the stream exitsthrough the center port 62. With only the turbulence transducer 58energized, the resultant turbulence causes the stream to attach to wall68 and to discharge through port 64. With both the turbulence transducer58 and the control port 72 in operation, the stream is directed to thefar wall 69 and to the outlet port 70. Since the wall attachment effectis self-sustaining in the presence of continued turbulence, the signalfrom control port 72 need not be continued to maintain the discharge atport 70.

In the symmetrical form actually illustrated in FIG. 2, a signal must besupplied from one of the control ports substantially concurrently withthe signal to the transducer 58 in order to make it certain that thestream is directed to the correct outlet port. When no cells areselected to be segregated from the stream, no signals are supplied tothe transducer 58 or to the valves and 82. In these circumstances, theflow remains laminar, and. the liquid is discharged through the centerport 62. However, upon the detection of a cell or parti cle of a firsttype to be segregated, signals are supplied substantially concurrentlyto the transducer 58 and to open the valve 82, respectively causing thestream to become turbulent, and providing a control port signal at 74causing the stream to be switched to the wall 68 and the outlet port 64.Upon the detection of a particle of a second category to be segregated,signals are supplied to the transducer 58 to initiate or maintainturbulence, and to open valve 80 to the control port 72,

causing the stream to switch to the wall 69 and the outlet port 70.Thus, in this embodiment, there. is the capability of sorting theparticles into three categories in a single pass through the apparatus.

In another alternative mode of operation, the transducer 58 remains onat all times, the stream is always turbulent, and switching of thestream is always exclusively controlled by the control ports 72 and 74so that the stream is always emitted either from the port 64 or the port70. The center port 62 is not used. Also, with the versatility providedby the modification of FIG. 2, there is presented the possibility ofachieving a faster response of the fluidic amplifier in terminating theturbulent flow to one of the nonaxial outlet ports, such as 64, when thetransducer is turned off, by concurrently providing a short signal fromthe associated control port 72. This sharply terminates the wallattachment at wall 68 while laminar flow is being re-established.

In the broader sense, the valves 80 and 82 may also be referred to aselectrical transducers. They perform the function of transducers in thatthey convert electrical signals to fluidic control signals which causethe switching of the liquid stream from one outlet port to another. Theswitching fluid used at the ports 72 and 74 should be compatible whichthe liquid in the main stream, but it need not be identical to theliquid. Thus, where the liquid in the main stream is water, theswitching fluid may be water, or air, or some other compatible fluid.

For the sake of simplicity in the drawing, the valves 80 and 82 areshown only schematically. However, it will be understood that they maybe electromagnetically operated valves, or they may operate on someother principle. For instance, they may be piezoelectric crystalactuated valves in which crystal movement in response to a voltageserves to open the valve. While not so illustrated, the valves 80 and 82are preferably built into the housing MA, as close as possible to theexits of the associated control ports 72 and 74. By this means, thetransit time of signals initiated through the valves is substantiallyreduced since the signals are transmitted substantially the entiredistance to the point of use by electrical means rather than by means ofa column of fluid.

It is possible to modify the embodiment of FIG. 2 to provide for atleast two more side ports corresponding to ports 64 and 70 by arrangingsuch ports in a circular pattern around the central port 62. Thus,another side port (not shown) can be arranged behind the central port62, and another one can be arranged in front of the central port 62.Such an arrangement requires the addition of appropriate valves andcontrol ports corresponding to the valves 80 and 82 and the controlports 72 and 74.

While not illustrated in the drawings of either of the FIGS. 1 or 2, theside outlet ports 64 and 70 may be provided with vent passages to reducethe pressure in the outlet ports to enhance the wall attachment effectand to reduce any possible impairment of the switching action whichmight be caused by a build-up of pressure in the receptacles to whichthe respective outlet ports are attached.

The embodiment of FIG. 2 provides greater versatility than theembodiment of FIG. 1, but the FIG. 1 embodiment is definitely preferred.One of the major advantages is that the control ports 72 and 74 are notrequired, and the problem of purging the switching chamber whendifferent samples are to be used, and when cleaning is required, isgreatly simplified by the elimination of these control ports.

In the embodiments of both FIGS. 1 and 2, the opticaldetection chamberis preferably composed of glass, and the switching chamber housing 14 or14A may preferablybe composed of a transparent synthetic resin material.While illustrated as separate housings which can be disassembled fromone another, it is obvious that these housings can be combined in aunitary structure.

gated according to a second particle characteristic into an outlet port164. If the particles are not so segregated, they continue on in themain stream outlet port 162 from the housing 114.

Thus, FIG. 3 illustrates the principle that a plurality of fluidicamplifier switches may be controlled to accomplish several sortingoperations based on signals obtained from a single optical chamber 10.In the operation of the system of FIG. 3, it will be understood that thedelay interval provided by the delay circuit 149 is appropriatelylengthened to accommodate for the additional interval required for theparticles to travel from the chamber 10 to the digital fluidic amplifier114.

FIG. 4 is a simplified schematic diagram illustrating the principle thattwo sets of the apparatus shown and described in connection with FIG. 1above can be connected in tandem to accomplish successive detection andsorting operations by two independent optical detections of particlecharacteristics accompanied by associated sorting operations. Thus, inFIG. 4, the combination of apparatus at the left side of the figurecorresponds precisely with the apparatus illustrated and de- Asillustrated in the simplified schematic diagram of FIG. 3, additionalfluidic amplifier switches may be employed downstream from the fluidicamplifier switch of the system of FIG. 1, or in that of FIG. 2. Thisprovides the possibility of still further sorting and segregation ofparticles on a single pass through the apparatus. The downstream fluidicamplifiers may also be connected to receive control signals fromcircuits 46.

FIG. 3, at the left side, illustrates in simplified schematic form anapparatus corresponding to the apparatus of FIG. 1, with correspondingparts correspondingly numbered. The main stream outlet port 62 isconnected to a second fluidic amplifier switch housing 114 which maycorrespond exactly in structure and operation with the fluidic switchcontained within the housing 14 and described above in connection withFIG. 1. The fliudic switch 114 responds to a signal from circuits 46 ona connectionindicated at 146 through a delay circuit 149 and a gatecircuit 151 to control a signal from an oscillator 153 to a transducerwithin the switch housing 114. By this means, particles which were notsorted and segregated in the first fluidic amplifier within housing 14,and diverted to the outlet port 64, continue on through the portconnection 62, through the switch 114, and may be sorted andsegrescribed above in connection with FIG. 1. The apparatus on the rightof the figure again duplicates the apparatus shown and described abovein connection with FIG. 1, all of the parts being numbered withcorresponding part numbers, but with a prefix digit 2 added to eachnumber. Thus, FIG. 4 illustrates the principle that a plurality of theapparatus combinations of FIG. 1 may be connected in tandem toaccomplish successive sorts on the same sample.

While the larger combinations illustrated in FIG. 3 and FIG. 4 are shownand described as being related to the apparatus of FIG. 1, it will bequite obvious that the principle of the use of multiple digital fluidicamplifiers and multiple combinations of sorting apparatus connected intandem may be applied as well to the apparatus of FIG. 2.

The invention has been described above entirely in terms of a liquidparticle carrying stream. While a liquid handling apparatus ispreferred, it will be understood that the principles of the inventioncan be employed with a gaseous fluid particle carrying stream using agas such as air.

While this invention has been shown and described in connection withparticular preferred embodiments, various alterations and modificationswill occur to those skilled in the art. Accordingly, the followingclaims are intended to define the valid scope of this invention over theprior art, and to cover all changes and modifications falling within thetrue spirit and valid scope of this invention.

We claim:

1. An improved particle sorting apparatus for sorting very smallparticles comprising a housing defining a detection chamber,

means for moving a fluid in which the particles are suspended throughsaid housing in a stream,

a detection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics,

sorting means positioned downstream from said detection chamber housing,

said sorting means being connected to said detection means and beingoperable in response to said electrical signals from said detectionmeans to segregate particles having predetermined differences inparticle characteristics from the stream of particles,

said particle sorting means defining at least two alternate paths ofegress of particles therefrom,

one of said paths representing particles segregated thereby and theother of said paths representing particles not to be segregated from thestream,

an indicating means coupled to receive signals from said particlecharacteristic detection means indicative of the presence of particlesto be sorted,

the combination of a light source and a photoelectric detectorassociated with one of said paths to determine the passage of particlestherethrough,

said indicating means being coupled to said photoelectric detector toreceive a signal therefrom in response to the passage of a particlethrough the path with which said photoelectric detector is associated,

said indicating means being operable in response to said last-mentionedsignal in correlation with the corresponding signal for that particlefrom said particle characteristic detection means to register thepassage of that particle through said path in order to verify thesorting operation of the apparatus.

2. A particle sorting apparatus as claimed in claim 1 wherein saidcombination of a light source and a photoelectricdetector is associatedwith the path of particles segregated by said particle sorting means.

3. A particle sorting apparatus as claimed in claim 1 wherein saidcombination of a light source and a photoelectric detector is associatedwith the path representing particles not to be segregated from thestream.

4. A particle sorting apparatus as claimed in claim 2 wherein a secondcombination of a light source and a photoelectric detector is associatedwith the path representing particles not to be segregated from thestream so that both paths are monitored to indicate which path eachparticle takes.

5. Apparatus as claimed in claim 1 wherein said indicating meanscomprises a cathode ray oscilloscope.

6. An improved particle sorting apparatus for sorting very smallparticles comprising a housing defining a detection chamber,

means for moving a fluid in which the particles are suspended throughsaid housing in a stream,

a detection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics,

sorting means positioned downstream from said detection chamber housing,

said sorting means being connected to said detection means and beingoperable in response to said electrical signals from said detectionmeans to segregate particles having predetermined differences inparticle characteristics from the stream of particles,

said particle sorting means defining at least two alternate paths ofegress of particles therefrom,

one of said paths representing particles segregated thereby and theother of said paths representing particles not to be segregated from thestream,

the combination of a light source and a photoelectric detectorassociated with one of said paths to determine the passage of particlestherethrough in order to verify the sorting operation of the apparatus,

an indicating means coupled to said photoelectric detector forregistering the passage of a particle through the path with which saidphotoelectric detector is associated,

said indicating means comprising a cathode ray oscilloscope,

said first mentioned detection means being connected to said cathode rayoscilloscope to provide a signal to initiate the operation of anoscilloscope sweep circuit in response to the passage of a particle atsaid first mentioned detection means,

and said oscilloscope being coupled to provide a visual indication ofthe signal from said last mentioned photoelectric detector on an axisperpendicular to the axis of the sweep obtained from said sweep circuit.

7. An improved particle sorting apparatus for sorting very smallparticles comprising a housing defining a detection chamber,

means for moving a fluid in which the particles are suspended throughsaid housing in a stream,

a detection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said difierences inparticle characteristics,

' sorting means positioned downstream from said detection chamberhousing, 5

said sorting means being connected to said detection means and beingoperable in response to said elec trical signals from said detectionmeans to segregate particles having predetermined differences inparticle characteristics from the stream of particles,

said particle sorting means defining at least two alternate paths ofegress of particles therefrom,

one of said paths representing particles segregated thereby and theother of said paths representing particles not to be segregated from thestream,

the combination of a light source and a photoelectric detectorassociated with one of said paths to determine the passage of particlestherethrough in order to verify the sorting operation of the apparatus,

said sorting means comprising a digital fluidic amplifier having aninlet connected to the outlet of said detection chamber to receive theparticle stream,

said fluidic amplifier including a switching chamber communicating withsaid inlet and at least two different outlet ports communicating withsaid switching chamber and defining said alternate paths of egress ofparticles therefrom,

said sorting means including an electrical transducer coupled to receiveelectrical signals from said detection means,

said fluidic amplifier being operable in response to signals receivedfrom said detection means through said electrical transducer to switchthe fluid particle carrying stream entering the inlet thereof from afirst outlet port representing one of said alternate paths to a secondselected outlet port representing the other of said alternate paths.

8. Apparatus as claimed in claim 7 wherein said housing defining saiddetection chamber is operable to provide for a laminar flow of theparticlevery small particlescomprising a housing defining a detectionchamber,

means for moving a fluid in which the particles are suspended throughsaid housing in a stream,

a detection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics,

sorting means positioned downstream from said detection chamber housing,

said sorting means being connected to said detection means and beingoperable in response to said electrical signals from said detectionmeans to segregate particles having predetermined differences inparticle characteristics from the stream of particles,

said particle sorting means defining at least two alternate paths ofegress of particles therefrom,

one of said paths representing particles segregated thereby and theother of said paths representing particles not to be segregated from thestream,

an indicating means coupled to receive signals from said particlecharacteristic detection means indicative of the presence of particlesto be sorted,

the combination of a light source and a photoelectric detectorassociated with said stream of particle carrying fluid down stream fromsaid detection means for providing an indication of the passage of aparticle therethrough,

said indicating means being coupled to said photoelectric detector toreceive a signal therefrom in response to the passage of a particlethrough the path with which said photoelectric detector is associated,

said indicating means being operable in response to said last mentionedsignal in correlation with the corresponding signal for that particlefrom said particle characteristic detection means,

and said indicating means being operable to measure the interval betweenthe signal from said particle characteristic detection means and thecorresponding signal from said photoelectric detector to thereby measurethe speed of a particle to be sorted as a basis for determining thetiming of the operation of said sorting means.

10. Apparatus as claimed in claim 9 wherein said combination of saidlight source and said photoelectric detector is positioned in thevicinity of said sorting means.

11. An improved particle sorting apparatus for sorting very smallparticles comprising a housing defining a detection chamber,

means for moving a fluid in which the particles are suspended throughsaid housing in a stream,

a detection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics,

sorting means positioned downstream from said detection chamber housing,

said sorting means being connected to said detection means and beingoperable in response to said electrical signals from said detectionmeans to segregate particles having predetermined differences inparticle characteristics from the stream of particles,

said particle sorting means defining at least two alternate paths ofegress of particles therefrom,

one of said paths representing particles segregated thereby and theother of said paths representing particles not to be segregated from thestream,

the combination of a light source and a photoelectric detectorassociated with said stream of particle carrying fluid down stream fromsaid detection means for providing an indication of the speed of aparticle to be sorted as a basis for determining the timing of theoperation of said sorting means,

an adjustable delay means connected between said detection means andsaid sorting means for providing an adjustment in the timing between theactuation of said detection means and the resulting signal to saidsorting means,

said delay being adjustable in accordance with the time intervaldetermined by said last mentioned photoelectric detector.

12. Apparatus as claimed in claim 11 wherein the signal from said lastmentioned photoelectric detector is coupled to said delay means todirectly control the operation of said delay means to provide foroperation of said sorting means after the correct interval of time.

13. An improved particle sorting apparatus for sorting very smallparticles comprising a housing defining a detection chamber,

means for moving a fluid in which the particles are suspended throughsaid housing in a stream,

a detection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics,

sorting means positioned downstream from said detection chamber housing,

said sorting means being connected to said detection means and beingoperable in response to said electrical signals from said detectionmeans to segregate particles having predetermined differences inparticle characteristics from the stream of particles,

said particle sorting means defining at least two alternate paths ofegress of particles therefrom,

cle to be sorted as a basis for determining the tim-- ing of theoperation of said sorting means,

said sorting means comprising a digital fluidic amplifier having aninlet connected to the outlet of said detection chamber to receive theparticle stream,

said fluidic amplifier including a switching chamber communicating withsaid inlet and at least two different outlet ports communicating withsaid switching chamber and defining said alternate paths of egress ofparticles therefrom,

said sorting means including an electrical transducer coupled to receiveelectrical signals from said detection means,

said fluidic amplifier being operable in response to signals receivedfrom said detection means through said electrical transducer to switchthe fluid particle carrying stream entering the inlet thereof from afirst outlet port representing one of said alternate paths to a secondselected outlet port representing the other of said alternate paths.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 2 8275Dated Auqust 6. 1974 Inventofls) LOUIS A. KAMENTSKY and ISAAC KLINGER Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Colunm 1. line 48, "vary" should read --very--'.

Column 3, line 13, "provided" should read provide--.

Column 8, 7 line 3, "circuits 47" should read circuits 46--;

line 30, "chamber '70" should read --chamber 60--.

Column 10, line 5 6, "which" should read --with--;

line 57, "the" should read -that--.

Signed and sealed this 5th day of November 1974.

(SEAL) Attest MCCOY M. GIBSON JR. l C. MARSHALL DANN Attesting OfficerCommissioner of Patents

1. An improved particle sorting apparatus for sorting very smallparticles comprising a housing defining a detection chamber, means formoving a fluid in which the particles are suspended through said housingin a stream, a detection means associated with said detection chamberfor detecting differences in particle characteristics and operable toprovide electrical signals which vary in accordance with saiddifferences in particle characteristics, sorting means positioneddownstream from said detection chamber housing, said sorting means beingconnected to said detection means and being operable in response to saidelectrical signals from said detection means to segregate particleshaving predetermined differences in particle characteristics from thestream of particles, said particle sorting means defining at least twoalternate paths of egress of particles therefrom, one of said pathsrepresenting particles segregated thereby and the other of said pathsrepresenting particles not to be segregated from the stream, anindicating means coupled to receive signals from said particlecharacteristic detection means indicative of the presence of particlesto be sorted, the combination of a light source and a photoelectricdetector associated with one of said paths to determine the passage ofparticles therethrough, said indicating means being coupled to saidphotoelectric detector to receive a signal therefrom in response to thepassage of a particle through the path with which said phOtoelectricdetector is associated, said indicating means being operable in responseto said lastmentioned signal in correlation with the correspondingsignal for that particle from said particle characteristic detectionmeans to register the passage of that particle through said path inorder to verify the sorting operation of the apparatus.
 2. A particlesorting apparatus as claimed in claim 1 wherein said combination of alight source and a photoelectric detector is associated with the path ofparticles segregated by said particle sorting means.
 3. A particlesorting apparatus as claimed in claim 1 wherein said combination of alight source and a photoelectric detector is associated with the pathrepresenting particles not to be segregated from the stream.
 4. Aparticle sorting apparatus as claimed in claim 2 wherein a secondcombination of a light source and a photo-electric detector isassociated with the path representing particles not to be segregatedfrom the stream so that both paths are monitored to indicate which patheach particle takes.
 5. Apparatus as claimed in claim 1 wherein saidindicating means comprises a cathode ray oscilloscope.
 6. An improvedparticle sorting apparatus for sorting very small particles comprising ahousing defining a detection chamber, means for moving a fluid in whichthe particles are suspended through said housing in a stream, adetection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics, sorting means positioned downstream from saiddetection chamber housing, said sorting means being connected to saiddetection means and being operable in response to said electricalsignals from said detection means to segregate particles havingpredetermined differences in particle characteristics from the stream ofparticles, said particle sorting means defining at least two alternatepaths of egress of particles therefrom, one of said paths representingparticles segregated thereby and the other of said paths representingparticles not to be segregated from the stream, the combination of alight source and a photoelectric detector associated with one of saidpaths to determine the passage of particles therethrough in order toverify the sorting operation of the apparatus, an indicating meanscoupled to said photoelectric detector for registering the passage of aparticle through the path with which said photoelectric detector isassociated, said indicating means comprising a cathode ray oscilloscope,said first mentioned detection means being connected to said cathode rayoscilloscope to provide a signal to initiate the operation of anoscilloscope sweep circuit in response to the passage of a particle atsaid first mentioned detection means, and said oscilloscope beingcoupled to provide a visual indication of the signal from said lastmentioned photoelectric detector on an axis perpendicular to the axis ofthe sweep obtained from said sweep circuit.
 7. An improved particlesorting apparatus for sorting very small particles comprising a housingdefining a detection chamber, means for moving a fluid in which theparticles are suspended through said housing in a stream, a detectionmeans associated with said detection chamber for detecting differencesin particle characteristics and operable to provide electrical signalswhich vary in accordance with said differences in particlecharacteristics, sorting means positioned downstream from said detectionchamber housing, said sorting means being connected to said detectionmeans and being operable in response to said electrical signals fromsaid detection means to segregate particles having predetermineddifferences in particle characteristics from the stream of particles,said particle sorting means definIng at least two alternate paths ofegress of particles therefrom, one of said paths representing particlessegregated thereby and the other of said paths representing particlesnot to be segregated from the stream, the combination of a light sourceand a photoelectric detector associated with one of said paths todetermine the passage of particles therethrough in order to verify thesorting operation of the apparatus, said sorting means comprising adigital fluidic amplifier having an inlet connected to the outlet ofsaid detection chamber to receive the particle stream, said fluidicamplifier including a switching chamber communicating with said inletand at least two different outlet ports communicating with saidswitching chamber and defining said alternate paths of egress ofparticles therefrom, said sorting means including an electricaltransducer coupled to receive electrical signals from said detectionmeans, said fluidic amplifier being operable in response to signalsreceived from said detection means through said electrical transducer toswitch the fluid particle carrying stream entering the inlet thereoffrom a first outlet port representing one of said alternate paths to asecond selected outlet port representing the other of said alternatepaths.
 8. Apparatus as claimed in claim 7 wherein said housing definingsaid detection chamber is operable to provide for a laminar flow of theparticle-suspending fluid therethrough, said electrical transducer beingoperable to convert the laminar flow to turbulent flow within saidfluidic amplifier switching chamber for selectively inducing turbulencein the stream of fluid in response to electrical signals from saiddetection means, said fluidic amplifier being operable in response tothe conversion of the stream of fluid from laminar flow to turbulentflow to switch the stream in said switching chamber from said firstoutlet port to said second outlet port.
 9. An improved particle sortingapparatus for sorting very small particles comprising a housing defininga detection chamber, means for moving a fluid in which the particles aresuspended through said housing in a stream, a detection means associatedwith said detection chamber for detecting differences in particlecharacteristics and operable to provide electrical signals which vary inaccordance with said differences in particle characteristics, sortingmeans positioned downstream from said detection chamber housing, saidsorting means being connected to said detection means and being operablein response to said electrical signals from said detection means tosegregate particles having predetermined differences in particlecharacteristics from the stream of particles, said particle sortingmeans defining at least two alternate paths of egress of particlestherefrom, one of said paths representing particles segregated therebyand the other of said paths representing particles not to be segregatedfrom the stream, an indicating means coupled to receive signals fromsaid particle characteristic detection means indicative of the presenceof particles to be sorted, the combination of a light source and aphotoelectric detector associated with said stream of particle carryingfluid down stream from said detection means for providing an indicationof the passage of a particle therethrough, said indicating means beingcoupled to said photoelectric detector to receive a signal therefrom inresponse to the passage of a particle through the path with which saidphotoelectric detector is associated, said indicating means beingoperable in response to said last mentioned signal in correlation withthe corresponding signal for that particle from said particlecharacteristic detection means, and said indicating means being operableto measure the interval between the signal from said particlecharacteristic detection means and the corresponding signal from saidphotoelectric detector to tHereby measure the speed of a particle to besorted as a basis for determining the timing of the operation of saidsorting means.
 10. Apparatus as claimed in claim 9 wherein saidcombination of said light source and said photoelectric detector ispositioned in the vicinity of said sorting means.
 11. An improvedparticle sorting apparatus for sorting very small particles comprising ahousing defining a detection chamber, means for moving a fluid in whichthe particles are suspended through said housing in a stream, adetection means associated with said detection chamber for detectingdifferences in particle characteristics and operable to provideelectrical signals which vary in accordance with said differences inparticle characteristics, sorting means positioned downstream from saiddetection chamber housing, said sorting means being connected to saiddetection means and being operable in response to said electricalsignals from said detection means to segregate particles havingpredetermined differences in particle characteristics from the stream ofparticles, said particle sorting means defining at least two alternatepaths of egress of particles therefrom, one of said paths representingparticles segregated thereby and the other of said paths representingparticles not to be segregated from the stream, the combination of alight source and a photoelectric detector associated with said stream ofparticle carrying fluid down stream from said detection means forproviding an indication of the speed of a particle to be sorted as abasis for determining the timing of the operation of said sorting means,an adjustable delay means connected between said detection means andsaid sorting means for providing an adjustment in the timing between theactuation of said detection means and the resulting signal to saidsorting means, said delay being adjustable in accordance with the timeinterval determined by said last mentioned photoelectric detector. 12.Apparatus as claimed in claim 11 wherein the signal from said lastmentioned photoelectric detector is coupled to said delay means todirectly control the operation of said delay means to provide foroperation of said sorting means after the correct interval of time. 13.An improved particle sorting apparatus for sorting very small particlescomprising a housing defining a detection chamber, means for moving afluid in which the particles are suspended through said housing in astream, a detection means associated with said detection chamber fordetecting differences in particle characteristics and operable toprovide electrical signals which vary in accordance with saiddifferences in particle characteristics, sorting means positioneddownstream from said detection chamber housing, said sorting means beingconnected to said detection means and being operable in response to saidelectrical signals from said detection means to segregate particleshaving predetermined differences in particle characteristics from thestream of particles, said particle sorting means defining at least twoalternate paths of egress of particles therefrom, one of said pathsrepresenting particles segregated thereby and the other of said pathsrepresenting particles not to be segregated from the stream, thecombination of a light source and a photoelectric detector associatedwith said stream of particle carrying fluid down stream from saiddetection means for providing an indication of the speed of a particleto be sorted as a basis for determining the timing of the operation ofsaid sorting means, said sorting means comprising a digital fluidicamplifier having an inlet connected to the outlet of said detectionchamber to receive the particle stream, said fluidic amplifier includinga switching chamber communicating with said inlet and at least twodifferent outlet ports communicating with said switching chamber anddefining said alternate paths of egress of particles therefrom, saidsorting means including an electrical transducer coupled to receiveelectrical signals from said detection means, said fluidic amplifierbeing operable in response to signals received from said detection meansthrough said electrical transducer to switch the fluid particle carryingstream entering the inlet thereof from a first outlet port representingone of said alternate paths to a second selected outlet portrepresenting the other of said alternate paths.